Process for the production of microfibrillated cellulose in an extruder and microfibrillated cellulose produced according to the process

Abstract

The present invention relates to a process for the production of microfibrillated cellulose wherein the process comprises the steps of, providing a slurry comprising fibers, adding the slurry to an extruder, treating the slurry in the extruder so that the fibers are defibrillated and microfibrillated cellulose is formed. The invention further relates to a microfibrillated cellulose produced.

Description

[0001]This application is a U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT / IB2010 / 054839, filed Oct. 26, 2010, which claims priority to U.S. Provisional Application No. 61 / 254,887, filed Oct. 26, 2009.FIELD OF THE INVENTION[0002]The invention relates to process for the production of microfibrillated cellulose by the aid of an extruder.BACKGROUND[0003]Cellulosic fibers are multi-component structures made from cellulose polymers, i.e. cellulose chains. Lignin, pentosans, hemicelluloses and other components known in art may also be present. The cellulose chains in the fibers are attached to each other to form elementary fibrils. Several elementary fibrils are bound to each other to form microfibrils and several microfibrils form aggregates. The links between the cellulose chains, elementary- and microfibrils are hydrogen bonds.[0004]Microfibrillated cellulose (MFC) (also known as nanocellulose) is a material made from wood cellulose fibers, agricultural r...

AI Technical Summary

Benefits of technology

[0008]It is an object of the present invention to provide a process for the production of microfibrillated cellulose in an improved way.

[0009]This object, as well as other objects and advantages, is achieved by the process according to claim 1. The invention relates to a process for the production of microfibrillated cellulose wherein the process comprises the steps of, providing a slurry comprising fibers, conducting the slurry to an extruder, treating the slurry in the extruder so that the fibers are defibrillated and microfibrillated cellulose is formed. In this way it has been shown that microfibrillated cellulose can be produced in a very energy efficient way.

[0010]At least one modifying chemical is preferably added to the extruder during treatment of the slurry, so that modified microfibrillated cellulose is formed. The use of an extruder for defibrillation of the fibers makes it possible to add a modifying chemical during defibrillation, i.e. at the same time. The design of the extruder thus allows both defibrillation of the fibers and mixing of the fibers with a chemical. Modified or functionalized microfibrillated cellulose can thus be produced in an improved and energy efficient way in a single process step.

[0014]The extruder is preferably a conical extruder. The use of a conical extruder is beneficial since the defibrillation of the fibers and mixing with an eventual chemical is very good and efficient.

[0015]The solid content of the slurry comprising the fibers being treated in the extruder may be above 30 wt %, preferably above 50 wt %. Due to the flow dynamics in the extruder, above all in a conical extruder, it is possible to increase the dry content of the slurry comprising the fibers to be treated.

Problems solved by technology

However, it is very energy consuming method to for example shred or refine the fibers and it is therefore not often used without combining the treatment with a pre- or post-treatment.